What differentiates elastic collisions from inelastic collisions?

Elastic collisions are characterized by the conservation of kinetic energy and momentum. During an elastic collision, both the total kinetic energy and total momentum of the system remain unchanged before and after the collision. This means that the energy is not transformed into other forms (like sound, heat, or deformation) but instead remains entirely as kinetic energy.

In contrast, inelastic collisions lead to a loss of kinetic energy, even though the momentum is still conserved. In such collisions, some portion of the kinetic energy is converted into other forms of energy, resulting in a decrease in the total kinetic energy of the colliding bodies.

The correct option captures this key difference: while kinetic energy is conserved in elastic collisions, it is not conserved in inelastic collisions. Understanding this distinction is crucial for problems involving collision dynamics, such as in physics and engineering contexts.